This invention relates to a process of preparing Ziegler-type catalyst components containing titanium and/or vanadium and magnesium, for the polymerization of .alpha.-olefins, by contacting an inert inorganic support successively with an organomagnesium compound and one or more compounds of titanium and/or vanadium.
The invention relates also to the polymerization of .alpha.-olefins having 2-8 carbon atoms, optionally together with an amount not exceeding 20 mole % of one or more other .alpha.-olefins having 2-15 carbon atoms, using these catalysts.
The use of such catalyst components is known from, for example, U.S. Pat. No. 3,787,384 where a support of silica, alumina or a mixture thereof is contacted with either a hydrocarbyl magnesium, a hydrocarbyl halogen magnesium, a hydrocarbyl aluminum, or a hydrocarbyl halogen aluminum compound, followed by an excess amount of a halogen compound of a transition metal, particularly titanium or vanadium.
Further, from German Patent Application No. 25 43 219 it is known to prepare a catalyst component by contacting silica with a magnesium compound and by contacting the resulting product with a titanium and/or vanadium compound.
From U.S. Pat. No. 4,173,547 catalyst components are known wherein a support material is contacted with an aluminum halogen compound, an organomagnesium compound, and a tetravalent titanium compound and/or a compound of another transition metal of group IV--IV in its highest valence, in the order given.
U.S. Pat. Nos. 3,993,588; 4,082,692; 4,087,380 and 4,256,865 disclose processes for preparing supported titanium and magnesium catalyst components involving the joint fluidization, in an inert gas stream and at a temperature of 150.degree.-1000.degree. C., of a silica support and a water-free magnesium halide or magnesium alkoxide compound, and the subsequent incorporation of a titanium compound in the product thus obtained.
With respect to each of the catalyst components noted above, the objective is to achieve the highest possible activity (i.e., the polymer yield per gram of active catalyst) as well as other suitable properties, particularly those regarding molecular weight distribution, particle size, and particle size distribution of the polymer powders obtained. Indeed, it is possible to achieve favorable polymer properties with these known catalyst components but their activity has proven to be substantially less than what was envisioned. It is additionally known (cf. R. Spitz et al, Eur. Pol. Journ., Vol. 15, pp. 441-444) that the activity of these catalysts strongly decreases during the copolymerization of ethylene with .alpha.-olefins having 3-10 carbon atoms, in particular hexylene, and that during the copolymerization considerable amounts of polymer waxes are produced which cause serious problems by depositing on the reactor wall.